A lighting film for letting sunlight into a room through, for example, a window of a building is proposed in PTL 1. In the lighting film, a plurality of unit prisms and flat surfaces are formed on one surface of an optically transparent support. Sunlight is let into a room through the unit prisms.
In the case of the above-described lighting film, however, light after passage through the lighting film may reach eyes of a person present in a room due to the effect of, for example, periodic motion of the sun. The light may cause glare, and the person in the room may feel discomfort. PTL 2 discloses a solar radiation shading control device which adjusts the opening degree of a blind on the basis of an index obtained from a particular mathematical formula for predicting glare such that the index has a value, at which glare does not cause discomfort.